"Whale mating call" from air filter box.

[n5ztw]

I just replaced head gaskets on my 2001 5L V8
I get a low pitched noise from the box containing the air filter.
This happens for 10-12 seconds after starting the engine and then every now and then. I also have intermittant slightly rough idle after warm-up.
Is it possible I have a leak on the gasket on the upper intake manifold?
Any ideas?
Bill

 

[deweyville65]

Loose seal and plugged air filter?

 

[n5ztw]

Replaced the Air Filter with a stock new one and the problem remains. Will look at the seal around the air filter box. Thanks
Bill

 

[Beargap]

A bad IAC (Idle Air Control) valve will make a moaning sound periodically. You can remove it and lubricate the valve mechanism, but they aren't too expensive to replace and easy to get at.

=Vic=